Bacterial Tracheitis

Etiology

Bacterial tracheitis is a bacterial infection of the trachea often preceded by a viral upper respiratory infection. The most common viruses implicated include Influenza A and B (type A being the most common), respiratory syncytial virus (RSV), parainfluenza virus, measles virus, and enterovirus.[2][3][4] These viruses cause airway mucosal damage via a local immune response which predisposes the trachea to the seeding of bacteria. Affected patients are usually healthy before onset, and most will recover with appropriate recognition and treatment. However, at-risk populations, including immunocompromised individuals, are prone to severe sequelae. Implicated bacteria include most commonly: Staphylococcus aureus (including methicillin-resistant Staphylococcus aureus [MRSA]), Streptococcus pneumoniae, Streptococcus pyogenes, Moraxella catarrhalis, Haemophilus influenzae type B (HiB), Haemophilus influenzae (non-typeable), and less commonly, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, and anaerobic organisms.[1][2][3][4]

The presence of a long-term tracheostomy is another potential predisposing factor for bacterial tracheitis, presumed to be a result of colonization of either a single bacterial species or multi-bacterial species from the tracheostomy tube in approximately 95% and 83% of respective cases.[3][5] The most common isolates in tracheostomy-dependent patients are S. aureus, Gram-negative bacilli, Pseudomonas aeruginosa, and Streptococcus pneumoniae. Meticulous tracheostomy care, including pulmonary toilet and scheduled changes of the inner cannula and the tracheostomy tube, are required to minimize the risk in this specific population.[3][6][7][8]

Epidemiology

The annual incidence of bacterial tracheitis varies between countries, with an estimated incidence of 0.1 to 1 case(s) per 100,000 children.[2][5][7] Bacterial tracheitis has a peak incidence between the ages of three to eight years old, although it has been described in both infants and adults. Recently, a shift in clinical course and incidence of bacterial tracheitis has been noted with the disease being less severe and occurring in an older subset of patients, typically five to ten years old.[7] Males have a slight predominance over females with various reported ratios from 1 to 1 to 5 to 1.[2] The incidence rises in the fall and winter months, and it is more infrequent in summer or spring, which coincides with the typical seasonal viral epidemics of influenza, parainfluenza, and respiratory syncytial virus (RSV).[2][3] Interestingly, one study of 33 pediatric tracheostomy-dependent patients at a large tertiary care center showed an association of bacterial tracheitis with higher socioeconomic status (SES); although they postulated that patients with lower SES do not present for treatment as frequently.[7]

Pathophysiology

In bacterial tracheitis, opportunistic bacteria invade damaged tracheal mucosa, made of pseudostratified columnar epithelium, and stimulate local and systemic inflammatory responses. In otherwise healthy patients, this is presumed to be precipitated by a viral upper respiratory infection, while in patients with an indwelling tracheostomy tube, it can also be due to seeding from a colonized tracheostomy appliance.[2][4] Local responses in the tracheal mucosa cause edema, thick mucopurulent secretions, ulceration, and mucosal sloughing, which can predispose the patient to subglottic narrowing, tracheal narrowing, and/or airway obstruction.[1] Systemic inflammation leading to sepsis is rare but can occur in immunocompromised patients. Staphylococcus aureus has been the most commonly implicated pathogen, although reports suggest M. catarrhalis is becoming more common, especially in younger children.[1][2][4]

Histopathology

Sputum, tracheal washings, or tracheal secretions can be sent for microscopic analysis, including gram stain, cell count, neutrophil count, aerobic cultures, anaerobic cultures, and/or fungal cultures. These usually reveal neutrophilia and the identification of bacterial species. Often, bacterial tracheitis is polymicrobial. Infection of the tracheal mucosa causes local inflammation, swelling, thick exudates, pseudomembranes, and necrosis of the larynx, trachea, and mainstem bronchi. A biopsy is rarely performed unless there is a concern for underlying malignancy or another neoplasm.[1][3]

History and Physical

Presentation of bacterial tracheitis can occur in various ways depending on the patient's age and whether or not they are tracheostomy-dependent. The most common presentation in non-tracheostomy-dependent children and adults is a more insidious development with prodromal symptoms that suggest a viral respiratory tract infection. Viral symptoms including rhinorrhea, post-nasal drip, cough, fever, myalgia, and sore throat are present up to a week before the acute worsening of the patient.[1][2][8] Patients will then develop acute airway deterioration, high fevers, hoarseness, toxic appearance, and increased mucopurulent secretions secondary to the bacterial infection. Less commonly, fulminant respiratory distress with less than 24 hours of symptoms can occur. Signs and symptoms include stridor (inspiratory or expiratory), fever, productive and painful cough, thick secretions, and tenderness of the trachea.[1][2][4][7][8] 

Drooling and tripoding are less common and suggest an alternative diagnosis such as epiglottitis, as children with bacterial tracheitis do not have as much difficulty swallowing their oral secretions. Patients with severe subglottic obstruction may have cyanosis, appear lethargic, or can be combative, suggesting hypoxemia and/or hypercarbia.[1][2]

In patients who are tracheostomy-dependent, symptoms of bacterial tracheitis can include high fevers, chills, productive cough, thick mucopurulent secretions, hemoptysis, peristomal skin breakdown or cellulitis, high ventilatory peak pressures, and/or tracheostomy obstruction.[2][3][5][7]

Evaluation

The diagnosis of bacterial tracheitis is primarily clinical via a thorough history and physical examination. As discussed above, patients may appear febrile, dyspneic, hoarse, stridulous, septic or toxic-appearing, and in respiratory distress.[2][7] Trial with nebulized epinephrine and glucocorticoids will typically fail to show improvement in the patient's clinical course.[1][2]

Laboratory investigation with white blood cell count is variable and nonspecific. Leukocytosis, as well as mild leukopenia, are commonly seen. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are also nonspecific but are estimated to be elevated in 68% of patients. Blood cultures are rarely positive; however, they should be obtained if there is suspicion for sepsis or if the patient is immunocompromised.[1][6]

Radiographic images of the lateral or anteroposterior neck can show subglottic or tracheal narrowing, typical of that seen with croup (steeple sign).[2][8] Less commonly, irregularity or haziness of the tracheal mucosal wall and air column can also be seen on lateral neck radiographs. This has been referred to as the "candle dripping" sign. The epiglottis should appear normal.[2] Overall, chest radiographs are of poor diagnostic value but can show findings suggestive of concurrent pneumonia, reported in roughly 50% of cases. The presence of concomitant pneumonia increases the severity of the disease and the probability of endotracheal intubation.[2] Computed tomography (CT) scans are typically not used during the diagnosis of pediatric patients but can be used in adults or in patients with suspected tracheal stenosis or recurrent tracheitis, who have respiratory stability.[3] Airway stabilization should be a priority before obtaining imaging in patients with severe respiratory symptoms or overt respiratory compromise.

Definitive diagnosis is made by direct visualization, although it is not necessary with strong clinical suspicion. Laryngoscopy and bronchoscopy allow visualization of the infected airway and will demonstrate a normal or mildly erythematous epiglottis and an erythematous, edematous trachea with thick mucopurulent exudates.[2][3] Bronchoscopy is performed with either a rigid or flexible endoscope, with the former suggested for suctioning the exudates to provide transient relief of airway obstruction as well as obtain specimens for culture. The decision to undergo bronchoscopy is made based on clinical severity. More severe cases benefit from the therapeutic stripping of exudates to provide relief of obstruction related to these secretions. Exudates can be thick secretions or pseudomembranes that adhere to the tracheal wall. Flexible bronchoscopy is an alternative for those patients with a less severe presentation. However, those patients without severe respiratory distress, hypoxia, and minimal tracheal abnormalities on radiograph can be managed without bronchoscopy initially.[2][3] Exudative secretions can extend distally to the mainstem bronchi. If bronchoscopy is performed, specimens for gram stain and cultures should be obtained during this time. Less severe cases not requiring endoscopy or endotracheal intubation can obtain cultures via a sputum sample. In practice, this can be difficult in children.

Diagnosis of bacterial tracheitis can be difficult given its rarity, in addition to more prevalent diseases with similar presentations. Epiglottitis can also present with fever, upper airway obstruction, and toxic appearance. However, these patients often present with drooling and a preference for the tripod position, which is uncommon in bacterial tracheitis. Croup can also present with stridor and similar radiographic presentation with subglottic narrowing (steeple sign). Bacterial tracheitis can be a complication of croup and should be suspected if therapeutic interventions such as nebulized racemic epinephrine or steroids do not improve the clinical course.[1] Peritonsillar or retropharyngeal abscesses will demonstrate fever, drooling, muffled voice changes, and pharyngeal pain with limited mobility of the neck. They also will not demonstrate the classic findings on X-ray. Other diseases that can mimic bacterial tracheitis are listed below but can include angioedema, foreign body aspiration, caustic ingestion, laryngeal malignancies, diphtheria, and severe bacterial pneumonia among others.[1][2]

Treatment / Management

Treatment of bacterial tracheitis includes a prompt assessment for airway compromise first. The need for intubation is common with reported rates ranging from 38% to 100% of patients in various studies.[1][2][8] This procedure can be difficult secondary to airway edema, and it is recommended to be performed in the operating room or intensive care unit setting by the most experienced teams available, with instruments ready for a potential surgical airway if intubation is unsuccessful. Hypoxia, respiratory muscle retractions, fatigue, altered mental status, and decreased breath sounds are signs indicative of impending airway failure. Younger children with smaller airways are at higher risk for the need for airway stabilization. If intubation is indicated, endotracheal tubes one or two sizes smaller than expected for the patient should be selected due to airway narrowing. Placement into the ICU after intubation is indicated to provide close monitoring and frequent suctioning of the endotracheal tube. In one case series, the average intubation duration was 3.2 days.[2][8] Extubation should be considered in those with clinical improvement, reduced tracheal secretions, and the development of an air leak around the endotracheal tube. Other treatments in less severe cases include supplemental humidified oxygen, racemic epinephrine trial, heliox, and reduced patient agitation, which can worsen an already compromised airway.[1][2][8](B2)

Antibacterial management should be prompt and include broad-spectrum coverage, including MRSA. Gram stain results, if obtained, can focus on antibiotic selection, but broad coverage should be initially chosen until culture results are obtained. Current guidelines recommend a 10-day to 14-day antibiotic course, although no formal studies have investigated the recommended time length of antimicrobial treatment. The first-line treatments suggested include amoxicillin-clavulanic acid, ceftriaxone plus nafcillin or vancomycin, clindamycin plus a third-generation cephalosporin, or ampicillin-sulbactam.[1][2][3] For patients with a true, severe, beta-lactam antibiotic allergy, the recommended antibiotic treatment regimen includes vancomycin or clindamycin plus levofloxacin or ciprofloxacin. (B2)

Glucocorticoids have not been shown to alter clinical course or patient outcomes.[1][2][8] Antiviral therapy may be beneficial if a preceding viral etiology is determined to be influenza and symptoms have been present for less than 48 hours. Routine, empiric antiviral treatment is not effective.[2](B2)

Differential Diagnosis

Bacterial tracheitis can be mimicked by many other disease processes including but not limited to:[1][2][3][4]

• Amyloidosis 
• Angioedema
• Candidiasis (laryngeal or tracheal)
• Caustic ingestion
• Deep neck space infection (DNSI)
• Diphtheria
• Epiglottitis
• Foreign body of aerodigestive tract
• Fungal laryngitis or tracheitis 
• Granulomatosis with polyangiitis (Wegner granulomatosis)
• Laryngeal hematoma
• Laryngeal trauma
• Laryngomalacia
• Laryngopharyngeal reflux (LPR)
• Laryngotracheobronchitis (croup)
• Leukoplakia
• Malignancy (esophageal, laryngeal, thyroidal, or tracheal)
  • Adenocarcinoma
  • Anaplastic thyroid cancer
  • Follicular thyroid cancer
  • Lymphoma
  • Medullary thyroid cancer
  • Melanoma
  • Metastasis
  • Papillary thyroid cancer
  • Squamous cell carcinoma
  • Thymic carcinoma
  • Thymoma
• Necrotizing sialometaplasia
• Peritonsillar abscess
• Pseudoepitheliomatous hyperplasia 
• Retropharyngeal abscess
• Sarcoidosis
• Subglottic stenosis
• Tracheal compression
• Tracheal stenosis
• Tracheostomy induced granulation
• Tracheostomy obstruction or decannulation
• Tracheomalacia
• Tuberculosis
• Viral laryngitis or tracheitis
• Vocal fold paresis/paralysis

Prognosis

Bacterial tracheitis is a life-threatening but very treatable disease process If evaluated and treated early enough in its course. In one review of 36 patients from 2018 in a tertiary care center, 69% of pediatric patients diagnosed with bacterial tracheitis were admitted to the pediatric intensive care unit (PICU), 43% required intubation, and one patient died from airway obstruction.[4] Regarding ventilatory dependent patients, when compared to those without lower respiratory infections, ventilated bacterial tracheitis patients had a significantly longer duration of mechanical ventilation and a greater length of stay in the ICU.[9] Children with tracheostomies diagnosed with bacterial tracheitis tend to have higher 30-day all-cause revisit rates than non-tracheostomy-dependent children.[6]

Complications

Complications of bacterial tracheitis include but are not limited to the following:[1][2][3][4][6][8][10]

• Acute respiratory distress syndrome (ARDS)
• Acute ventilatory dependent respiratory failure (AVDRF)
• Airway obstruction
• Anoxic encephalopathy 
• Aspiration pneumonia
• Cardiopulmonary arrest
• Cellulitis
• Death 
• Disseminated intravascular coagulation
• Hypoxia
• Intubation
• Pneumonia 
• Pulmonary edema 
• Systemic inflammatory response syndrome (SIRS), sepsis, septic shock
• Tracheostomy
• Tracheal stenosis
• Toxic shock syndrome